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MOYAPA01 | Laser-plasma Wakefield Acceleration: Concepts, Tests and Premises | electron, plasma, acceleration, target | 10 | ||||
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The presentation will review all novel methods presently developed to reach high accelerating fields from the concepts, to simulations, feasibility demonstration in real tests and performances presently achieved. It will point out and compare their potential but also their technical challenges and possible limitations. It will also present the necessary R&D and the tests presently envisaged including schedule and milestones not only in terms of fields but also of beam quality preservation and power efficiency. Finally, possible future applications will be suggested.
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Transparencies
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MOZBPA01 | Results from the VUV-FEL | radiation, electron, FEL, undulator | 34 | ||||
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The talk will provide the latest results from the VUV-FEL. It will cover the general performance of the machine and comparison to theory. A status will be given of the performance of key systems: the gun, accelerating modules and RF systems, electron and photon beam diagnostics, timing and synchronization and undulator performance. Future developments and implementations will also be discussed (and implications to the XFEL).
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Transparencies
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MOPCH002 | Seeding the FEL of the SCSS Phase 1 Facility with the 13th Laser Harmonic of a Ti: Sa Laser Produced in Gas | FEL, undulator, radiation, SASE | 44 | ||||
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A seeding configuration, in which the 13th harmonic (60 nm) of a Ti: Sa laser (50 mJ, 10 Hz, 130 fs) generated in a gas cell is used as the external source, will be tested in 2006 on the SCSS test facility (SPring-8 Compact Sase Source, Japan). This facility is based on a thermionic cathode electron gun (1 nC of bunch charge), a C-band LINAC (5712 MHz, 35 MV/m) and two in-vacuum undulators (15 mm of period). The maximum electron beam energy is 250 MeV and the SASE emission from visible to 60 nm can be obtained. The High order Harmonic Generation (HHG) experiment was mounted off-line at the end of last December. A first chamber is dedicated to harmonic generation. A second one is used for spectral selection and adaptation of the harmonic waist in the modulator. The tests are performed in Saclay with the LUCA (Laser Ultra Court Accordable) laser (15 mJ, 10 Hz, 50 fs) from January to March at 266 nm, 160 nm and 60 nm and its results are presented here. Also, before performing the real tests in SPring-8 FEL presence, final theoretical estimations of the performances relying on 1D simulations using PERSEO code and 3D simulations using GENESIS and SRW codes are given.
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MOPCH003 | Seeding SPARC Facility with Harmonic Generation in Gases: Preliminary Tests of the Harmonic Generation in Gas Chamber | undulator, FEL, electron, radiation | 47 | ||||
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In High Gain Harmonic Generation Free Electron Laser configuration, an external light source is injected in the first part of an undulator. The electron-photon interaction leads to a coherent light emission in the second part of the undulator. We propose to use the High Order Harmonic Generation in gases process as the seed for SPARC project (Frascati, Italy). With this facility, the electron beam is accelerated to 200 MeV and passes through an undulator of 6 sections. The preliminary tests on the seeding chambers presented in this paper have been realised at the CEA (Saclay, France). The experiment is based on three vacuum chambers. In the first one, a Ti: Sa laser (800 nm, 2.5 mJ, 50 fs, 10 Hz) is focussed in a 10 Hz pulsed gas jet (Argon or Xenon), producing harmonics of the fundamental. Filters in the second chamber enable the selection of the harmonic (3rd or 5th). Finally, a telescope focuses the harmonic beam at a given position. The whole module is to be moved to the SPARC facility. Appropriate tuning of the undulator gaps will amplify the 3rd and 5th harmonics seeded, as well as non-linear harmonics of those wavelengths, allowing the perspective of producing a FEL at 53 nm
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MOPCH004 | Coherent Harmonic Generation Experiment on UVSOR-II Storage Ring | electron, storage-ring, undulator, klystron | 50 | ||||
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Harmonic Generation schemes on Free Electron Laser devices are very promising. The injection of a traditional laser source inside the first undulator leads to an efficient energy modulation of the electron bunch, and therefore, its spatial modulation, resulting in a more coherent light emission along the second undulator. Experiments have been performed on the UVSOR-II Storage Ring at Okazaki (Japan) with electrons stored at an energy of 600 MeV, and using a 2.5 mJ Ti:Sa laser at 800 nm wavelength, 1 kHz repetition rate, and 100 fs up to 2 ps pulse duration. The experimental setup is presented, including the transport alignment and synchronisation between the laser and the electron beam. The third harmonic at 266 nm has been characterised versus various parameters: current, RF cavity voltage, undulator gap, magnetic functions of the storage ring, and laser pulse duration. Those results are compared with theory via analytical models and simulations.
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MOPCH005 | The ARC-EN-CIEL FEL Proposal | emittance, radiation, undulator, FEL | 53 | ||||
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ARC-EN-CIEL (Accelerator-Radiation Complex for Enhanced Coherent Intense Extended Light), the French project of a fourth generation light source aims at providing the user community with coherent femtosecond light pulses covering from UV to soft X ray. It is based on a CW 1 GeV superconducting linear accelerator delivering high charge, subpicosecond, low emittance electron bunches with a high repetition rate (1 kHz). Electron beam calculations will be presented. The FEL is based on the injection of High Harmonics Generated in Gases (HHG) in a High Gain Harmonic Generation scheme, leading to a rather compact solution. The produced radiation extending down to 0.8 nm with the Non Linear Harmonics reproduces the good longitudinal and transverse coherence of the harmonics in gas. Calculations are preformed with PERSEO, taking into account the proper transverse overlap between HHG and the electron beam, and with SRW. Optional beam loops are foreseen to increase the beam current or the energy. They will accommodate fs synchrotron infrared Coherent Synchrotron Radiation sources, VUV and X ray ranges and a FEL oscillator in the 10 nm range. An important synergy is expected between accelerat
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MOPCH007 | Undulators for a Seeded HGHG-FEL Test Bench at MAX-lab | undulator, electron, FEL, radiation | 59 | ||||
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Undulators for a Seeded HGHG-FEL at MAX-lab Within the European FEL Design Study a seeded HGHG-FEL will be set up at MAX-lab. In the modulator, a planar pure permanent magnet undulator, the 3rd harmonic of a Ti:Sapphire laser (267nm) interacts with the electron beam. In the following dispersive section the energy modulation is converted into a spatial modulation. The radiator emits at the third harmonic (89nm). The radiator has an APPLE II type magnetic structure providing full polarization control. The undulators and the dispersive section are currently built at BESSY. The electron beam height at MAX-lab of 400mm requires a specific design of the undulator carriages. The magnetic and mechanical design of the HGHG stage will be presented.
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MOPCH008 | Considerations for Double Pulse Lasing from the BESSY-FEL | FEL, electron, simulation, bunching | 62 | ||||
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BESSY proposes a linac-based High-Gain Harmonic-Generation (HGHG) free electron laser (FEL) facility with three independent FEL lines. Two to four HGHG stages downconvert the initial seed wavelength (230nm to 460nm) to the desired radiation range (1.24nm to 51nm). High FEL gain is ensured as the seed radiation interacts only with unperturbed parts of the electron bunch in every HGHG-stage. This so-called fresh-bunch-technique relies on dipole chicanes that delay the electron bunches relative to the radiation. Fresh-bunch chicanes are incorporated prior to each modulator in the BESSY-FEL allowing the bunch to completely travel through all undulators. However, simulations show that bunch parts that have previously lased generate a noticeable radiation power level in the final amplifiers. This motivated simulation studies on the significance and applicability of such inherent additional pulses. It is revealed that the BESSY-FEL provides the opportunity to deliver double pulses at the FEL exit being of high interest to the user community. Temporal seperation and intensity levels can be controlled by carefully optimising the properties of the magnetic chicanes.
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MOPCH009 | The BESSY 2nd Generation Soft X-ray FEL User Facility | FEL, radiation, undulator, controls | 65 | ||||
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Future VUV-to-soft-X-ray FEL facilities promise to open fundamentally new frontiers for the synchrotron user community. So-called 2nd generation FELs, which use seeded schemes rather than SASE, can deliver reproducible ultra-short photon pulses at an energy level of mJ/pulse. BESSY has been designing a High-Gain-Harmonic-Generation (HGHG) based FEL with a 2.3 GeV superconducting driver linac that covers photon energies from 24 eV to 1 keV. The design provides full tuneability of photon energy, variable beam polarization and complete synchronization to external lasersall essential for future femtosecond, time-resolved pump-probe experiments. Also, the CW linac offers great flexibility for the repetition rates and pulse patterns. BESSY-organized User Workshops helped identify the user requirements for such an FEL. This information provided the basis for the Technical Design Report that was submitted to the German Wissenschaftsrat in 2004, which then held an on-site review in 2005. Meanwhile, preparatory studies continue at BESSY. They include start-to-end simulations, tolerance studies, and the development of superconducting RF technology in the HoBiCaT test facility.
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MOPCH011 | Jitter Measurement by Spatial Electro-optical Sampling at the Flash Free Electron Laser | electron, FEL, diagnostics, polarization | 71 | ||||
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For pump-probe experiments carried out at the VUV-FEL at DESY, FEL laser pulses with 32 nm wavelength have to be synchronized with high precision to optical laser pulses generated by a TiSa oscillator. To measure the relative timing variations between the FEL and the optical laser, an electro-optical experiment to determine the electron beam arrival time at the undulator has been installed. Here, the electron beam profile is encoded spatially into the laser pulse and readout by an intensified camera. A similar experimental setup has been successfully used at the sub-picosecond pulsed source (SPPS) at higher charge and shorter rms bunch length. In this paper, we report about the achievements and difficulties of the Timing Electro-Optical (TEO) setup, that allows to post-order experimental user data with a precision of 100 fs rms and better.
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MOPCH019 | Baseline Design of the Linac Upgrade for Fermi | linac, FEL, controls, ELETTRA | 92 | ||||
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The FERMI FEL requires a major upgrade of the existing linac, which needs to be transformed from being the injector for the ELETTRA light source, to becoming the source for the FERMI FEL. In this work, we present the baseline design, including the integration of the 7 additional systems from the LIL linac, and one X-band station as linearizers. We will present the new layout with the required modifications and additions to the existing infrastructure to meet the more demanding needs of the system. Such modifications include a new RF controller, improvements in the modulator stability and an upgrade to the average power capabilities of the system to operate at 50 Hz. Test results from the characterization of the existing systems will be included, as well as plans for future development.
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MOPCH024 | Future Seeding Experiments at SPARC | FEL, undulator, radiation, resonance | 95 | ||||
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Sources based on High order Harmonics Generated in gases (HHG) with high power Ti:Sa lasers pulses represent promising candidates as seed for FEL amplifiers for several reasons, as spatial and temporal coherence, wavelength tunability and spectral range, which extends down to the nm wavelength scale. This communication describes the research work plan that is under implementation at the SPARC FEL facility in the framework of the EUROFEL programme. The main goal of the collaboration is to study and test the amplification and the FEL harmonic generation process of an input seed signal obtained as higher order harmonics generated both in crystals (400 nm and 266 nm) and in gases (266 nm, 160 nm, 114 nm). The SPARC FEL can be configured to test several cascaded FEL layouts that will be analysed in this contribution.
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MOPCH025 | Laser Comb: Simulations of Pre-modulated E- Beams at the Photocathode of a High Brightness RF Photoinjector | gun, electron, cathode, simulation | 98 | ||||
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A density modulated beam at the photocathode though the proper modulation of the laser beam pulse does not change substantially emittance and energy spread, properties directly related to FEL. It has been found that bunch density modulation is transformed into energy modulation along the propagation through the injector*. There are some physical arguments that suggest a possibility to use this modulation for the enhancement of the FEL process, or for the production of plasma wakes. Preliminary beam dynamics studies have been carried on to explore the use of electron beam pre-modulation at the cathode to adjust their longitudinal structure at the end of the beamline. Energy modulation at the end of the beamline could eventually be turned into current modulation through a magnetic compressor with R56<0. The feasibility of this experiment has to be investigated carefully, preliminary studies are discussed here. This paper focuses on simulations that explore the properties of the energy modulation at the end of the beamline correlated to the initial characteristics of the train of electron pulses.
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*M. Biagini et al. Beam Dynamics Studies for the SPARC Project, Proc. of PAC03. |
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MOPCH027 | Metal Film Photocathodes for High Brightness Electron Injectors | cathode, gun, vacuum, target | 104 | ||||
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Advanced high brightness injectors require photocathodes with fast response,high quantum efficiency and good surface uniformity. Both Mg films deposited by laser ablation and Pb films deposited by vacuum arc could satisfy these requirements. Their emission and morphology are compared.
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MOPCH029 | Status of the SPARC Project | emittance, gun, undulator, electron | 110 | ||||
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The SPARC Project is starting the commissioning of its photo-injector. RF gun, RF sources, RF network and control, power supplies, emittance meter, beam diagnostics and control to measure the RF gun beam are installed. The photocathode drive laser has been characterized in terms of pulse shape and quality. We expect to conduct beam measurements at RF gun exit in the next future and consequently to start the installation of accelerating sections. The design of the 12 m undulator for the FEL experiment has been completed and the first undulator section out of 6 is under construction: we expect to characterize it at Frascati ENEA laboratory within the next months. SPARC as a facility will host FEL experiments using SASE, seeding and non-linear resonant harmonics. Additional R&D on X-band and S-band structures for velocity bunching are in progress, as well as studies on new photocathode materials and exotic undulator designs. We also present studies on solenoid field defects, beam based alignments, exotic electron bunch production (blow-out of short laser pulses or intensity modulated laser pulses). The possible use of segmented superconducting micro-undulators will be discussed too.
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MOPCH030 | Production of Coherent X-rays with a Free Electron Laser Based on an Optical Wiggler | radiation, electron, emittance, FEL | 113 | ||||
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The interaction between high-brightness electron beams and counter-propagating laser pulses produces X rays via Thomson scattering. If the laser source is long enough, the electrons bunch on the scale of the emitted X-ray wavelength and a regime of collective effects establishes. In this case, the FEL instability develops and the system behaves like a FEL based on an optical undulator. Coherent X-rays are irradiated, with a bandwidth thinner than that of the incoherent emission. The emittance of the beam and gradients or irregularities in the laser energy distribution are the principal factors that limit the growth of the X-ray signal. We analyse with a 3-D code the transverse effects in the emission produced by a relativistic electron beam when it is under the action of an optical laser pulse and the X-ray spectra obtained. The scalings typical of the optical wiggler, with very short gain lengths and overall time durations of the process make possible considerable emission also in violation of the Pellegrini criterion for static wigglers. A generalized form of this criterion is validated on the basis of the numerical evidence.
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MOPCH034 | On a Skeleton CASSINI Ovals Current Undulator | undulator, electron, radiation, free-electron-laser | 119 | ||||
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A new undulator structure for free electron lasers was presented. Current skeleton CASSINI ovals produced magnetic fields which are spatially periodic. The current structure was in the shape of stacks of modified CASSINI ovals. The current has alternating directions. The magnetic field components for each wire present C2 symmetry. CASSINI undulator transverse cross-section* was approximated by polygons. In cartesian coordinates the Biot-Savart law was analytically evaluated. The magnetic field was mainly transversal and easily adjusted with the current. The versatility of this structure introduces a new type of two beams longitudinal undulator or wiggler design for transverse moments.
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*Cassini curve; C. Mihu, I.P. Iambor-1989. |
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MOPCH043 | An Optimization Study for an FEL Oscillator at TAC Test Facility | FEL, electron, radiation, undulator | 136 | ||||
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Recently, conceptual design of the Turkic Accelerator Center (TAC) proposal was completed. The main goal of this proposal is a charm factory that consists of a linac-ring type electron-positron collider. In addition, synchrotron radiation from the positron ring and free electron laser from the electron linac are proposed. The project related with this proposal has been accepted by the Turkish government. It is planned that the Technical Design Report of TAC will have been written in the next three years. In this period, an infrared oscillator free electron laser (IR FEL) will be constructed as a test facility for TAC. 20 and 50 MeV electron energies will be used to obtain infrared FEL. The main parameters of the electron linacs, the optical cavities and the FEL were determined. The possible use of obtained laser beam in basic and applied research areas such as biotechnology, nanotechnology, semiconductors and photo chemistry were discussed.
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MOPCH045 | A Source of Coherent Soft X-ray Radiation Based on High-order Harmonic Generation and Free Electron Lasers | FEL, undulator, electron, simulation | 142 | ||||
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We examine a scheme for a Free Electron Laser (FEL) harmonic amplifier seeded by a ~30-nm wavelength signal produced using a process of High-order Harmonic Generation (HHG). The seed is first amplified in an optical klystron from ~100 kW to ~30 MW using a 1 GeV electron beam and then is used for an energy modulation of electrons in the downstream undulator. Subsequently, a 100-MW level of radiation at shorter wavelengths down to 4 nm is obtained by bunching the energy modulated electrons and passing the bunched beam through an undulator tuned to the desired harmonic of 30 nm. We also compare this scheme to a more familiar harmonic cascade FEL by replacing the HHG with an additional stage of harmonic generation.
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MOPCH047 | Study of the Electron Beam Dynamics in the FERMI @ ELETTRA Linac | electron, emittance, linac, simulation | 145 | ||||
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A study of the electron beam dynamics in the linac is made within the framework of the design of a free electron laser (FEL) at the Syncrotrone Trieste*. A scope of the work includes analysis of two operational scenarios, one with relatively long electron bunches of the order of 1.5 ps and a moderate peak current of 500 A and one with shorter bunches of the order of 0.7 ps and higher peak current of the order of 800 A. In both cases, care has been taken to preserve the slice and projected emittances formed in the photocathode gun injector and to minimize the slice energy spread. The latter goal is accomplished by balancing the onset of the microbunching instability driven by the longitudinal space charge forces and the emission of coherent synchrotron radiation using Landau damping produced by a so-called laser heater. Various analytical techniques and tracking codes have been employed to obtain the reported results.
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*C. Bocchetta, et al., this conference. |
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MOPCH051 | Operation of the First Undulator-based Femtoslicing Source | electron, photon, background, radiation | 154 | ||||
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At the BESSY II storage ring, a source of sub-100-fs x-ray pulses with tunable polarization and excellent signal-to-background ratio has been constructed in 2004, based on laser-induced energy modulation ("femtoslicing"*) and subsequent angular separation of the short-pulse x-rays from an elliptical undulator. After commissioning and characterizing the source, short-pulse radiation is now routinely delivered for pump-probe applications. The paper summarizes the results from commissioning and operational experience as well as possible upgrade options.
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*A. Zholents and M. Zoloterev, PRL 76 (1996), 912. |
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MOPCH056 | Development of High Brightness Soft X-ray Source Based on Inverse Compton Scattering | electron, background, MCP, scattering | 166 | ||||
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Compact soft X-ray source based on inverse compton scattering have been developed at Waseda University. Using 1047nm laser light from Nd:YLF laser scattered off 4.2MeV electron beam generated from a photo-cathode rf-gun, we have already suceeded to generate the soft X-ray. The energy of this x-ray is included in the part of water window, in which absorption of water is much less than that of moleculars that organize a living body. Furthermore, this x-ray source has other features such as short pulse, proportional mono-energy and energy variableness. Because of these tures, the application to the biological microscope have been expected. However, the flux of x-ray is not satisfied for the biological microscope application. Therefore, to multiply a soft X-ray flux, we utilized multi-pass amplifier for the laser light and improved a collision chamber. In this conference, we will report the experimental results and future plans.
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MOPCH057 | The Design of a 1.8 keV Compton X-ray Generator for a SC RF Linac at KAERI | electron, photon, linac, brilliance | 169 | ||||
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A quasi-monochromatic X-ray source based on the KAERI SC linac system has been designed and is being manufactured now. A 10 MeV 10 mA electron beam together with a 20 W 1.06 ?m laser beam will be used for 1.8 keV Compton X-ray generation with a few percentage of energy spread and 107 photons per second. A simple straight beamline was designed to deliver the electron beam with no degradation of its emittance and energy spread and to focus it to a proper size to produce the desired X-rays. We expect the first demonstration of 1.8 keV Compton X-ray generation in autumn 2006.
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MOPCH069 | Lattice Design for the Fourth Generation Light Source at Daresbury Laboratory | linac, FEL, undulator, electron | 184 | ||||
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The proposed Fourth Generation Light Source (4GLS) has three electron transport paths, an energy recovery loop containing the main linac, IDs and a VUV-FEL, a separate branch after the main linac for an XUV-FEL and a transport path for an IR-FEL. The first two present major challenges in lattice design. The energy recovery loop will be fed by a high average current gun, with bunches of charge of about 80 pC. High charge (1nC) bunches from a high brightness gun will be accelerated prior to the main linac and split into the XUV-FEL branch using energy separation after the main linac. We present a lattice design and results from numerical modelling of the electron bunch transport. The requirements of the machine are short bunches, a small emittance for both branches and an overall topology which gives a reasonable dimension for the building. Different transport and compression schemes were assessed to meet these requirements whilst balancing the disruptive effects of longitudinal and transverse space charge, CSR, wakefields and BBU. Investigations into all of these instabilities are summarized together with other transport issues and the resulting requirements on all IDs.
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MOPCH088 | Ion Cooler Storage Ring, S-LSR | ion, electron, proton, beam-cooling | 237 | ||||
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Ion cooler and storage ring, S-LSR has been constructed. Its beam commissioning has been successfully performed since October, 2005 and electron beam cooling for 7 MeV proton beam has been performed with both flat and hollow spatial distributions. Effect of relative velocity sweep between electron and ion beams on the cooling time* has been confirmed. Based on the success to create the peaks in the energy spectrum of laser-produced ions, injection of laser-produced ions into S-LSR after rotation in the longitudinal phase space by an RF cavity synchronized to the pulse laser is under planning in order to apply electron cooling for such real laser produced hot ions. Three dimensional laser cooling satisfying the condition of 'tapered cooling' is also under investigation. 24Mg+ ions are to be laser-cooled only in the 'Wien Filter' in order to be cooled down to the appropriate energy according to their horizontal positions**. In parallel with the computer simulation, construction of the laser cooling system with use of ring dye laser accompanied with the second harmonics generator is now underway.
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*H. Fadil et al. Nucl. Instr. & Meth. in Phys. Res. A517, 1-8 (2004).**A. Noda and M. Grieser, Beam Science and Technology, 9, 12-15 (2005). |
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MOPCH168 | Novel Development on Superconducting Niobium Film Deposition for RF Applications | plasma, cathode, vacuum, ion | 457 | ||||
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A new deposition technology has been developed, based on a cathodic arc system working under UHV conditions, to produce metallic thin films. The technique presents several advantages compared to standard sputtering, mainly: ionized state of the evaporated material, absence of gases to sustain the discharge, higher energy of atoms reaching the substrate surface, possibility to apply bias to the substrate and to guide the arc plasma using magnetic fields. Recent results on superconducting Niobium films deposited under several conditions and on sapphire substrate are reported. A cavity deposition system has been developed and the plasma transport to the cavity cell studied
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MOPCH178 | Tests on MgB2 for Application to SRF Cavities | SLAC, target, LANL, cryogenics | 481 | ||||
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Magnesium diboride (MgB2) has a transition temperature (Tc) of ~40 K, i.e., about four times higher than niobium (Nb). The studies in the last three years have shown that it could have about one order of magnitude less RF surface resistance (Rs) than Nb and seems much less power dependent compared to high-Tc materials such as YBCO. In this paper we will present results on the dependence of Rs on surface magnetic fields and possibly the critical RF surface magnetic field.
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MOPCH195 | The LiCAS-RTRS A Survey System for the ILC | survey, simulation, vacuum, CERN | 520 | ||||
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The ILC requires an unprecedented accuracy and speed for the survey and alignment of its components. The Rapid Tunnel Reference Surveyor (RTRS) is a self-propelled train intended to automatically survey a reference network in the ILC tunnels with a design accuracy of 200 microns over distances of 600 m. A prototype RTRS has been built by the LiCAS collaboration. It will shortly commence operation at DESY. The operation principle of the RTRS will be explained. The status of the project's hardware, software and calibrations as well as the principles and performance of the underlying measurement techniques will be described.
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MOPLS080 | A Laser-wire System at the ATF Extraction Line | electron, photon, extraction, optics | 738 | ||||
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A new laser-wire system has been installed at the ATF extraction line at KEK, Tsukuba. The system aims at a micron-scale laser spot size and employs a mode-locked laser system. The purpose-built interaction chamber, light delivery optics, and lens systems are described, and the first results are presented.
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MOPLS081 | A Study of Laser System Requirements for Application in Beam Diagnostics and Polarimetry at the ILC | diagnostics, controls, luminosity, optics | 741 | ||||
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Advanced laser systems will be essential for a range of diagnostics devices at the ILC. High average power, excellent stability and reliability will be crucial in order to deliver the information required to attain the necessary ILC luminosity. The key parameters are listed together with the R&D required to achieve the necessary laser system performance.
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MOPLS098 | Study of an ILC Main Linac that Follows the Earth Curvature | emittance, linac, alignment, quadrupole | 786 | ||||
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In the base line configuration, the tunnel of the ILC will follow the earth curvature. The emittance growth in a curved main linac has been studied, including static and dynamic imperfections. These include effects due to current ripples in the power supplies of the steering coils, the impact of the beam position monitor scale errors.
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MOPLS114 | Construction of the Probe Beam Photo-injector of CTF3 | emittance, gun, vacuum, simulation | 828 | ||||
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The paper describes the HF and dynamic beam modelling performed onto the 3 GHz / 2,5 cells photo-injector of the future CTF3 (CLIC Test Facility 3) probe beam linac, whose goal is to demonstrate the feasibility of the 30 GHz accelerating sections in the framework of the CLIC project. The Probe Beam Photo-Injector (PBPI) conception is inspired from the drive beam photo-injector already designed by LAL (Orsay, France) and actually tested in our laboratory. However, the design of PBPI has been simplified with respect to the previous because the charge per bunch is 4 times lower and the number of bunches several orders of magnitude smaller. The internal geometry and the coupling system of the PBPI have been designed with 2D (SUPERFISH) and 3D (HFSS, ANSYS) codes. A detailed analysis of the dissymmetry (induced by the coupling system) of the accelerating field component has been performed. Based on the modified design, PARMELA simulations showed that the technical specifications are fulfilled. The vacuum issue has been also carefully investigated, and NEG (Non Evaporated Getter) technology has been adopted in order to reach the 10-10 mbar pressure inside the structure.
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MOPLS128 | Status of the Fatigue Studies of the CLIC Accelerating Structures | CLIC, CERN, target, radio-frequency | 858 | ||||
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The need for high accelerating gradients for the future Compact Linear Collider imposes considerable constraints on the materials of the accelerating structures. The surfaces exposed to high pulsed RF currents are subjected to cyclic thermal stresses possibly resulting in surface break up by fatigue. Since no fatigue data exists in the literature up to very large numbers of cycles, a comprehensive study has been initiated. Low cycle fatigue data (up to 108 cycles) has been collected by means of a pulsed laser surface heating apparatus. The surface damage has been characterized by SEM observations and roughness measurements. High cycle fatigue data (up to 1011 cycles) at various stress ratios have been collected in high frequency bulk fatigue tests using an ultrasonic apparatus. It is found that the appearance of surface fatigue damage in the laser experiments, and of fatigue cracks in the bulk specimen, happen at similar stress levels for similar numbers of cycles. This allows the two experimental techniques to be connected and to predict the surface damage at a high number of cycles. Up-to-date fatigue data for selected high conductivity, high strength Cu alloys are presented.
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MOPLS130 | Implications of a Curved Tunnel for the Main Linac of CLIC | linac, emittance, quadrupole, CLIC | 864 | ||||
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Preliminary studies of a linac that follows the earth's curvature are presented for the CLIC main linac. The curvature of the tunnel is modeled in a realistic way by use of geometry changing elements. The emittance preservation is studied for a perfect machine as well as taking into account imperfections. Results for a curved linac are compared with those for a laser-straight machine.
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TUYPA01 | Femtosecond Bunch Length Measurements | radiation, diagnostics, electron, CDR | 915 | ||||
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The measurement of ultrashort longitudinal bunch profiles is of growing importance to accelerator development and operation. With requirements of ~10fs time resolution, and a desire for non-destructive and real time diagnostics, the challenges for diagnostic development are significant. Alongside more established transverse deflecting cavity and CTR measurement techniques, new approaches arriving from the field of ultrafast lasers offer significant potential; Ultrafast electro-optic detection has now been demonstrated on several accelerators, and in many distinct forms, although challenges remain in getting to the desired time resolution. Proposed schemes combining ultrafast laser diagnostics with FEL interactions, such as the "optical replica" scheme also have considerable potential. Here, an overview of the current status of femtosecond scale longitudinal profile diagnostics will be given, together with an outlook to the future expectations.
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TUYPA03 | Developments in Beam Instrumentation and New Feedback Systems for the ILC | feedback, damping, KEK, controls | 925 | ||||
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This presentation will review the challenging beam properties that need to be measured and controlled and new diagnostic developments that address these challenges for ILC beam instrumentation.
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TUOAFI03 | Production of MeV Photons by the Laser Compton Scattering Using a Far Infrared Laser at SPring-8 | FIR, photon, electron, storage-ring | 961 | ||||
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In order to produce MeV gamma-ray by the Laser Compton scattering (LCS), a high power optically pumped Far Infrared (FIR) laser has been developed at SPring-8. In the case of the SPring-8 storage ring, the momentum acceptance is so large (± 200 MeV) that the scattered electron is re-accelerated, then the stored beam is not lost by the LCS process. The beam diagnostics beamline is used to inject a FIR laser beam against 8-GeV stored electron beam and to extract MeV gamma-ray produced by LCS. The FIR laser system, gamma-ray production system, and measured gamma-ray spectrum will be presented. Future plans will also be introduced. In order to produce higher intense gamma-ray, we are constructing new gamma-ray production system at another beamline.
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Transparencies
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TUOCFI02 | First Results of SNS Laser Stripping Experiment | ion, proton, electron, SNS | 980 | ||||
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Thin carbon foils are used as strippers for charge exchange injection into high intensity proton rings. However, the stripping foils become radioactive and produce uncontrolled beam loss, which is one of the main factors limiting beam power in high intensity proton rings. Recently, we presented a scheme for laser stripping of an H- beam for the SNS ring. First, H- atoms are converted to H0 by a magnetic field, then H0 atoms are excited from the ground state to the upper levels by a laser, and the excited states are converted to protons by a magnetic field. This paper presents first results of the SNS laser stripping proof-of-principle experiment. The experimental setup is described, and possible explanations of the data are discussed.
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Transparencies
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TUPCH019 | Laser-based Beam Diagnostic for the Front End Test Stand (FETS) at RAL | electron, ion, emittance, dipole | 1037 | ||||
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High power proton accelerators (HPPA) are required for several future projects like spallation sources or a neutrino factory. Compared with existing machines the beam power therefore has to be increased by a factor of 30. The Front end test stand at RAL is being built to demonstrate that a chopped Hminus beam of 60 mA at 3 MeV with 50 pps and sufficiently high beam quality, as required for all proposed Proton drivers, can be built. For the test stand a comprehensive set of beam diagnostics is also required. Due to the high beam energy and power non destructive diagnostic methods are favorable. Hminus beams offer the possibility to use intense laser light to detach the additional electron and use the produced particles for beam diagnostics. The principle is appropriate to determine the transversal beam density distribution as well as the transversal and longitudinal beam emittance in front and behind the RFQ. A detailed layout of the beam diagnostics including a discussion of the predicted spatial and temporal resolution and the dynamic range of the proposed devices will be presented.
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TUPCH021 | Principles of longitudinal beam diagnostics with coherent radiation | electron, radiation, DESY, diagnostics | 1040 | ||||
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The Kramers-Kronig dispersion relation connects the real and imaginary part of a response function under very general assumptions. It is used in the context of accelerator physics for longitudinal bunch diagnostics as a phase retrieval technique: the modulus of the complex form factor (the Fourier transform of the charge distribution) is accessible experimentally, and the missing phase then (partially) reconstructed to allow an inversion of the Fourier transform. Contrary to real and imaginary part, the connection between modulus and phase is not unique anymore due to the possibility of zeros of the form factor in the complex frequency plane that cannot be measured. This paper gives a mathematically explicit, step-by-step derivation of the phase reconstruction technique for bunch diagnostics, and it explains the problem of zeros and their practical effect with some examples. The intention is not utmost mathematical rigour, but a clear, accessible explanation of all steps involved.
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TUPCH022 | Large Horizontal Aperture BPM for use in Dispersive Sections of Magnetic Chicanes | pick-up, simulation, electron, SMA | 1043 | ||||
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A beam position monitor with a large horizontal aperture for use in dispersive sections of FLASH magnetic chicanes will be installed in October 2006. It has a horizontal range of 13 cm and a resolution requirement of better than 10 microns. A stripline design mounted perpendicularly to the the electron beam direction is used to provide broadband electrical pulses traveling in opposite directions, the phases of which give a measure of the beam position. The phase measurement will be accomplished through an optical method developed for a beam arrival time monitor. Results from simulation and recent beam arrival-time measurements will be used to justify expectations for the BPM performance.
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TUPCH024 | Comparative Study of Bunch Length and Arrival Time Measurements at FLASH | electron, SASE, FEL, DESY | 1049 | ||||
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Diagnostic devices to precisely measure the longitudinal electron beam profile and the bunch arrival time require elaborate new instrumentation techniques. At the VUV-FEL, two entirely different methods are used. The bunch profile can be determined with high precision by a transverse deflecting RF structure. The method is disruptive and does not allow to monitor multiple bunches in a macro-pulse train. Therefore, it is augmented by two non-disruptive electro-optical devices, called EO and TEO. The EO setup uses a dedicated diagnostic laser synchronized to the machine RF. The longitudinal electron beam profile is encoded in the intensity profile of a chirped laser pulse and analyzed by looking at the spectral composition of the pulse. The second setup, TEO, utilizes the TiSa-based laser system used for pump-probe experiments. Here, the temporal electron shape is encoded into a spatial dimension of laser pulse by an intersection angle between the laser and the electron beam at the EO-crystal. In this paper, we present a comparative study of bunch length and arrival time measurements performed simultaneously with all three experimental techniques.
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TUPCH025 | Precision RF Gun Phase Monitor System for the VUV-FEL | gun, electron, acceleration, power-supply | 1052 | ||||
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For RF photo-injectors, the properties of the high brightness beam critically depend on the synchronization between the RF gun acceleration phase and the photo-cathode laser. At the VUV-FEL, the phase stability is determined by operating the RF gun close to zero-crossing RF phase. This allows the conversion of phase variations into charge variations which then is readout by a precision charge measurement system based on toroids. In this paper, we discuss the limitation of this method. Resolution reduction of the charge measurement system due to electro-magnetic-interference is discussed in detail.
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TUPCH026 | Single Shot Longitudinal Bunch Profile Measurements at FLASH using Electro-optic Techniques | electron, linac, SASE, FEL | 1055 | ||||
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For the high-gain operation of a SASE FEL, extremly short electron bunches are essential to generate sufficiently high peak currents. At the superconducting linac of the VUV-FEL at DESY, we have installed an electro-optic experiment with temporal decoding and spectral decoding to probe the time structure of the electric field of single sub 200fs e-bunches. In this technique, the field-induced birefringence in an electro-optic crystal is encoded on a chirped ps laser pulse. The longitudinal electric field profile of the electron bunch is then obtained from the encoded optical pulse by a single-shot cross correlation with a 30 fs laser pulse using a second-harmonic crystal (temporal decoding) or by a single-shot measurement of its spectrum (spectral decoding). In the temporal decoding measurements an electro-optic signal of 230fs FWHM was observed, and is limited by the material properties of the particular electro-optic crystal used. Bunch profile and time jitter measurements were obtained simultaneously with VUV SASE operation.
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TUPCH027 | Time Resolved Single-shot Measurements of Transition Radiation at the THz Beamline of FLASH using Electro-optic Spectral Decoding | radiation, electron, FEL, DESY | 1058 | ||||
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Single-shot electro-optic detection was used to measure the temporal profile of coherent transition radiation (CTR) pulses at the VUV-FEL at DESY. The CTR was generated from single bunches kicked to an off-axis screen, with the radiation transported through a 20m long transfer line imaging the CTR from a radiation screen to an experimental station outside the accelerator tunnel. Bipolar pulses with a FWHM less than 1ps have been measured and are consistent with simulations of the propagation of radiation through the transfer line.
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TUPCH028 | Layout of the Optical Synchronization System for FLASH | electron, diagnostics, feedback, DESY | 1061 | ||||
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The present RF synchronization system of the VUV-FEL can typically stabilize the arrival time of the electron bunches at the undulator to about 200 fs on a timescale of minutes and to several picoseconds on a timescale of hours. To improve the machine stability and to ensure optimal performance for the VUV-FEL user facility, a new ultra-precise timing system is mandatory. The optical synchronization system under construction will satisfy three goals: Firstly, it provides a local oscillator frequency with the same stability as the existing low-level RF regulation, secondly, it can synchronize the experimental lasers of the FEL users with a precision in the order of 30 fs, thirdly, it provides an ultra-stable reference for beam arrival time measurements and enables a feedback on the electron beam to compensate residual drifts and timing jitter. The optical synchronization system is based on an optical pulse train from a mode-locked laser with a highly stabilized repetition rate. This paper describes the proposed layout of the optical synchronization system, the integration into the machine layout and the diagnostic experiments to monitor the performance of the system.
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TUPCH029 | High-precision Laser Master Oscillators for Optical Timing Distribution Systems in Future Light Sources | feedback, FEL, linac, DESY | 1064 | ||||
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X-ray pulses with a pulse duration in the 10 fs regime or even less are needed for numerous experiments planned at next generation free electron lasers. A synchronization of probe laser pulses to the x-ray pulses with a stability on the order of the pulse width is highly desirable for these experiments. This requirement can be fulfilled by distributing an ultra-stable timing signal to various subsystems of the machine and to the experimental area to provide synchronization at the fs level over distances of several kilometers. Mode-locked fiber lasers serve as laser master oscillators (LMO), generating the frequencies required in the machine. The pulse train is distributed through length-stabilized fiber links. This paper focuses on the LMO, devoting special attention to the phase noise properties of the frequencies to be generated, its reliability to operate in an accelerator environment, and the residual timing jitter and drifts of the RF feedback for the fiber links. A prototype experimental system has been constructed and tested in an accelerator environment and its performance characteristics will be evaluated.
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TUPCH041 | Electro-optic Diagnostics on the Daresbury Energy Recovery Linac | electron, CSR, free-electron-laser, diagnostics | 1094 | ||||
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An electro-optic longitudinal bunch profile monitor is being implemented on the 4GLS prototype energy recovery linac (ERL/p) at Daresbury Laboratories and will be used both to characterise the electron bunch and to provide a testbed for electro-optic techniques. The electro-optic station is located immediately after the bunch compressor, and within the FEL cavity; its location allows it to draw on nearby beam profile monitors and CTR and CSR diagnostics for calibration and benchmarking. We discuss the implementation and planned studies on electro-optic diagnostics with this diagnostic station.
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TUPCH048 | A Study of Emittance Measurement at the ILC | emittance, electron, quadrupole, coupling | 1115 | ||||
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The measurement of the ILC emittance in the ILC beam delivery system and the linac is simulated. Estimates of statistical and machine-related errors are discussed and implications for related diagnostics R&D are inferred.
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TUPCH049 | Proposal for a Fast Scanning System Based on Electro-optics for Use at the ILC Laser-wire | electron, focusing, positron, PETRA | 1118 | ||||
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Electro-optic devices open the possibility of ultra-fast scanning systems for use in intra-train scanning at the ILC, where scanning rates in excess of 100 kHz may be required. A first study of the possibilities is presented together with the first results from a prototype system.
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TUPCH050 | Beam Profile Measurements with the 2-D Laser-wire | electron, photon, PETRA, injection | 1121 | ||||
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A new laser-wire system has been installed at the PETRA ring at DESY, Hamburg. The system is set up to scan in two dimensions using piezo-driven mirrors and employs a newly acquired injection seeded Q-switched laser. The system is described and first results are presented.
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TUPCH074 | Fast and Precise Beam Energy Monitor Based on the Compton Backscattering at the VEPP-4M Collider | photon, electron, collider, scattering | 1181 | ||||
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Accurate knowledge of the colliding beam energies is essential for the current experiments with the KEDR \cite{KEDR} detector at the VEPP-4M collider. Now the experimental activity is focused on the new precise measurement of the tau-lepton mass by studying the behavior of the tau production cross-section near the reaction threshold. To achieve the desired quality of the experiment, an on-line beam energy monitoring by the Compton backscattering of laser light was performed. This approach is found to be a very good supplement to rare energy calibrations by the resonant depolarization technique, saving the beam time for luminosity runs. The method itself does not require electron beam polarization and additionally allows one to measure the electron beam energy spread. The achieved accuracy of the method in the beam energy range 1.71.9 GeV is 60 keV.
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TUPCH081 | Technical Aspects of the Integration of the Optical Replica Synthesizer for the Diagnostics of Ultra-short Bunches in FLASH at DESY | electron, undulator, DESY, vacuum | 1199 | ||||
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In this paper we present an overview of current status of the Optical Replica synthesizer at DESY. The method is based on producing an "optical copy" of the electron bunch with its subsequent analysis with optical techniques*. To this end, a near-IR laser beam is superimposed on the electron beam in the first undulator of an optical klystron. In the following dispersive section the laser-induced energy modulation is transformed into a density modulation . The modulated electron bunch then produces a strong optical pulse in the second undulator. Analysis of this near-IR pulse (the optical copy) then provides information about the profile, the slice emittance and the slice energy spread of the electron bunch. We discuss the implementation of such a measurement set-up at the FLASH facility at DESY and investigate the influence of various parameters on the performance of the device. Topics we address include the dispersive chicane, as well as the requirements for the seed laser pulses and the detection and analysis of the near-IR pulse.
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*E. Saldin, et al. "A simple method for the determination of the structure of ultrashort relativistic electron bunches," Nucl. Inst. and Methods A 539 (2005) 499. |
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TUPCH094 | THz Diagnostic for the Femtosecond Bunch Slicing Project at the Swiss Light Source | electron, SLS, storage-ring, CSR | 1229 | ||||
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Interaction of electron bunches with a femtosecond Ti:Sa laser beam along a modulator wiggler in the Swiss Light Source (SLS) storage ring results in an energy modulation of the electron beam on the length scale of the laser pulse. While high energy photon pulses (3 18 keV, ~ 100 fs long) are produced by an in-vacuum undulator (radiator) and used for time resolved experiments within the SLS femtosecond bunch slicing project, coherent synchrotron radiation (CSR) emitted by the adjacent bending magnet in the THz-regime is used for longitudinal slicing diagnostics and monitoring of slicing efficiency. This paper describes the simulation and layout of the THz-diagnostic beamline and presents first time and spectrally resolved measurements with the longitudinal slicing diagnostics, which has been set-up for the SLS femto-slicing project.
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TUPCH103 | New Developments on Single-shot Fiber Scope | SLAC, controls, feedback | 1253 | ||||
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New development has been done to reduce the noise and improve the stability of the single-shot fiber scope, which used an optical fiber recirculating delay line to regenerate the single-shot very short electrical pulse, so a sampling scope can recover the original signal. New measurements have been done and will be reported.
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TUPCH151 | ERLP/4GLS Low Level Radio Frequency System | controls, ERLP, linac, feedback | 1376 | ||||
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The Energy Recovery Linac Prototype (ERLP) being constructed at Daresbury Laboratory will use an analog-based low level RF (LLRF) control system designed and built at FZR Rossendorf. Once the machine is operational, the testing and development of a digital LLRF feedback system will take place using the ERLP as a testbed.
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TUPCH163 | Status of 30 GHz High Power RF Pulse Compressor for CTF3 | CTF3, CLIC, vacuum, linac | 1405 | ||||
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A 70 ns 30 GHz pulse compressor with resonant delay lines has been built and installed in the CTF3 test area to obtain the high peak power of 150 MW necessary to demonstrate the full performance of the new CLIC accelerating structure. This pulse compressor will be commissioned at high power in 2006. Different methods to provide fast RF phase switching are discussed. The current status of the CTF3 RF pulse compressor commissioning and first results are presented.
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TUPCH188 | Phase Stability of the Next Generation RF Field Control for VUV- and X-ray Free Electron Laser | klystron, electron, controls, free-electron-laser | 1453 | ||||
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For pump and probe experiments at VUV- and X-ray free electron lasers the stability of the electron beam and timing reference must be guaranteed in phase for the injector and bunch compression section within a resolution of 0.01 degree (rms) and in amplitude within 1 10-4 (rms). The performance of the field detection and regulation of the acceleration RF directly influences the phase and amplitude stability. In this paper we present the phase noise budget for a RF-regulation system including the noise characterization of all subcomponents, in detail down-converter, ADC sampling, vector-modulator, master oscillator and klystron. We study the amplitude to phase noise conversion for a detuned cavity. In addition we investigate the beam jitter induced by these noise sources within the regulation and determine the optimal controller gain. We acknowledge financial support by DESY Hamburg and the EUROFEL project.
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TUPCH191 | Considerations for the Choice of the Intermediate Frequency and Sampling Rate for Digital RF Control | controls, feedback, DESY, simulation | 1462 | ||||
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Modern FPGA-based rf control systems employ digital field detectors where an intermediate frequency (IF) in the range of 10 to more than 100 MHz is sampled with a synchronized clock. Present ADC technology with 14-16 bit resolution allows for maximum sampling rates up to 250 MHz. While higher IF's increase the sensitivity to clock jitter, lower IF frequencies are more susceptible to electromagnetic noise. The choice of intermediate frequency and sampling rate should minimize the overall detector noise, provide high measurement bandwidth and low latency in field detection, and support algorithms for optimal field estimation.
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TUPLS055 | First Section of a 352 MHz Prototype Alvarez DTL Tank for the CERN SPL | quadrupole, linac, CERN, proton | 1621 | ||||
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In the Linac4/SPL projects at CERN, 352 MHz 30 mA DTL Alvarez accelerating structure will be used to accelerate protons between 3 and 40 MeV. The R&D for the development of a prototype structure for the energy range from 3 to 10 MeV is taking place jointly at ITEP and VNIIEF. The design of this 2.7 m Alvarez tank containing 27 drift tubes is described in this document. Results of calculations of the section parameters are presented. One of the main features of the design is the use of permanent magnets made of SmCo5 alloy as quadrupole focusing lenses (PMQ) inside the drift tubes. Details of the experimental PMQ-equipped drift tube are described.
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TUPLS065 | Beam Commissioning of Ion Cooler Ring, S-LSR | ion, electron, proton, vacuum | 1642 | ||||
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S-LSR is a new ion cooler ring constructed in Kyoto University. The circumference is 22.557 m and the maximum magnetic rigidity is 1 Tm. The constructiion and the vacuum baking had been finished in September, 2005. The beam commissioning was started since October, 2005. The injected beam is 7 MeV proton from the existing linac. The beam circulation test and the electron beam cooling were carried out successfully and the beam information and the characteristics of the ring were measured. One of the subjects of S-LSR is a realization of the crystalline beams using the electron and laser cooling. The lattice of S-LSR was designed to suppress the beam heating as much as possible and we also present such measurement results in this paper.
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TUPLS093 | AG Acceleration using DPIS | ion, target, rfq, plasma | 1720 | ||||
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We are investigating high current and high repetition rate ion production methods for various heavy ions which can be utilized for an injector of an FFAG accelerator. Direct Plasma Injection Scheme (DPIS) is one of the candidates of the ion production methods and to confirm the capability of the DPIS, we are now preparing for accelerating high intensity Ag15+ ions. The DPIS uses a combination of Laser Ion Source (LIS) and RFQ linac. The plasma goes into the linac directly without transportation line and the ions are extracted at RFQ entrance. To determine the specifications of new RFQ electrodes, the plasma properties were measured. With the Nd-glass laser (3 J / 30 ns), we could not obtain high charge state ions. A new Nd-YAG laser (2.3 J / 6 ns) enabled us to observe many high charged ions and the most produced ions were Ag15+. We completed the plasma distribution measurements. Based on these results, we designed the new RFQ, which will accommodate Q / M = 1 / 8 particles, supposing Ag+15.
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TUPLS097 | Application of DPIS to IH Linac | plasma, linac, target, ion | 1729 | ||||
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We are now designing a Laser Ion Source (LIS), which will be operated with an Inter-digital H (IH) structure linac using the Direct Plasma Injection Scheme (DPIS). The DPIS has been applied to RFQ linacs and has successfully achieved very high current with simple structure. The IH structure linac was designed to accept 40 keV proton beam which could be produced by the DPIS. The combination of the DPIS and IH structure linac will realize quite compact accelerator complex with intense proton beam. The detailed design study of a plasma production chamber with a cryogenic cooler is investigated.
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TUPLS100 | Generation of Highly Charged Ions Using ND-glass Laser | ion, target, plasma, vacuum | 1735 | ||||
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The parameters of ions (charge state distributions, currents and pulse durations) were measured in laser plasma generated by 3 J/30 ns Nd-glass laser for wide range of elements from 12C to 181Ta and for different laser power densities at the target surface. It is shown that such a laser can effectively generate highly charged ions for elements from 12C to 56Fe. Registered ion charge states significantly drops for heavier elements because of recombination losses of highly charged ions during laser produced plasma expansion into vacuum. Absolute currents and numbers of ions with different charge states were obtained by normalization of charge state distributions summary on total ion currents measured by Faraday cup for 1011 W/cm2 and 1012 W/cm2 laser power densities at the target surface. The results obtained are very useful for Laser Ion Source (LIS) development, in particular, for Direct Plasma Injection Scheme (DPIS) study*.
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*M. Okamura et al. Laser and Particle Beams, 20, 2002, pp. 451 - 454. |
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WEPCH006 | Comparison between Simulations and Measurements of Low Charge Electron Bunch in the ELSA Facility | simulation, electron, quadrupole, ELSA | 1927 | ||||
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Dedicated focal spot size measurements carried out at the ELSA electron linear accelerator facility have provided detailed data which are suitable for benchmarking of different simulation codes for high charge bunch beam acceleration issued from an RF photo-injector source. We present some characteristic features of bunched electron beam propagation from beam formation at the photo-cathode to acceleration through RF cavities until the final focussing on a target, by using numerical simulations obtained with MAGIC, PARMELA, MAFIA, PARTRAN tool box codes. The challenges for the planned benchmarking are discussed.
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WEPCH097 | Beam Dynamics in Compton-ring Gamma Sources | electron, synchrotron, emittance, simulation | 2143 | ||||
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Electron storage rings with a laser cavity are promising intensive sources of polarized hard photons to generate polarized positron beams. The dynamics of electron bunches circulating in a storage ring and interacting with high-power laser pulses is studied both analytically and by simulation. Common features and difference in the bunch behavior interacting with an extremely high power laser pulse (polarized positron source for the ILC project) and a moderate pulse (source for CLIC) are shown. Also considerations on particular lattice designs for both rings are presented.
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WEPCH147 | Simulations of Electron Effects in Superconducting Cavities with the VORPAL Code | electron, simulation, plasma, radio-frequency | 2269 | ||||
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Modeling the complex boundaries of superconducting radio frequency (SRF) accelerating cavities on a Cartesian grid is a challenge for many Finite Difference Time Domain (FDTD) electromagnetic PIC codes. The simulation of such cavities require conformal (curve fitting) boundaries. Modeling the full cavity including couplers and ports is fundamentally a three dimensional problem requiring capability to run in parallel on large numbers of processors. We have recently added conformal boundaries using the method of Zagorodnov* to the plasma simulation code VORPAL. Using this higher order boundary algorithm and the surface physics package TxPhysics, we have begun studies of self-consistent electron effects in SRF cavities. We have modeled the beam excitation of cavity modes and the effects of electron multipacting. Results from these studies will be presented using the new user friendly visualization tool that now ships with VORPAL.
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*I. A. Zagorodnov et al. A uniformly stable conformal FDTD-method in Cartesian grids, International Journal of Numerical Modeling 16, 127 (2003). |
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WEPCH166 | Beam Test of Thermionic Cathode X-band RF-gun and Linac for Monochromatic Hard X-ray Source | electron, photon, linac, cathode | 2319 | ||||
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A compact hard X-ray source based on laser-electron collision is proposed. The X-band linac is introduced to realize a very compact system. 2MeV electron beam with average current 2μampere at 10 pps, 200 ns of RF pulse is generated by a thermionic cathode X-band RF-gun. Beam acceleration and X-ray generation experiment by the X-band beam line are under way.
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WEPCH172 | Electron Beam Pulse Processing toward the Intensity Modified Radiation Therapy (IMRT) | electron, radiation, cathode, gun | 2334 | ||||
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Radiation therapy attracts attention as one of the cancer therapies nowadays. Toward the next generation of the intensity modified radiation therapy (IMRT), the processing of electron beam pulse is studied using a photo cathode RF gun linac. Accelerated electron pulses will be converted to x-ray pulses by a metal target bremsstrahlung method or by a laser inverse Compton scattering method. Recently, the radiation therapy of cancer is developing to un-uniform irradiation as IMRT. A photo cathode RF gun is able to generate a low emittance electron beam pulse using a laser light pulse. We thought that a photo cathode RF gun can generate intensity and shape modified electron beam by processing of incident laser light. Because of a low emittance, an electron pulse is able to accelerate keeping shape. Electron beam processing by photo masks in incident optical system and generated beams are reported here. Images on photo masks were transported to a cathode surface by optical relay imaging. Beams were monitored by Desmarquest (Cr:Al2O3) luminescence. Spatially separation of a spot to a spot is about 0.3mm. Modified electron beam has fine spatial resolution.
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WEPCH178 | Simulation Study of Compact Hard X-ray Source via Laser Compton Scattering | electron, linac, simulation, focusing | 2346 | ||||
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The compact hard X-ray source via laser Compton scattering between high intensity electron beam and high power laser beam was developed at FESTA (The Femtosecond Technology Research Association) project in collaboration between AIST and SHI. According to completion of the project in March 2005, the compact hard X-ray source is being transferred from FESTA to AIST to upgrade and to apply the system to biological and medical uses. Our system consists of a laser-driven photocathode rf gun, two 1.5m-long S-band accelerator structures and a high power Ti:Sa Laser system. This system can generate a hard X-ray pulse which has variable energy of 12 keV 33 keV with narrow bandwidth by changing electron energy and collision angle. Maximum X-ray photon yield at FESTA was accomplished about 107photons/s (@10Hz, MAX 33keV) in case of 165 degree collision angle. In the next phase, we are planning to make the total system much compact using X-band or C-band accelerator structures with permanent magnets. We have carried out the numerical simulations to investigate the possibility of these compact systems. In this conference, we will talk about results of the simulations and future plans.
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WEPCH181 | Ion Implantation Via Laser Ion Source | ion, plasma, target, extraction | 2355 | ||||
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We report on the development of a new implantation technique via laser ion source. By applying a high voltage on the accelerating gap, this compact device was able to accelerate towards a substrate ions from ablation plasma. The occurrence of arcs during the extraction phase was a major problem to overcome. A pulsed KrF laser was utilized to produce plasma by ablation of solid targets. Radiation wavelength and pulse duration were 248 nm and 20 ns, respectively. The laser beam, 70 mJ per pulse, was focused onto different targets in a spot of about 1 mm2 in surface, obtaining an irradiance value of about 3.5 x 108 W/cm2. The implanted samples were characterized by energy dispersive x-ray spectroscopy, Rutherford backscattering spectrometry and x-ray photoelectron spectrometry. Implantations of Al, Cu and Ge on Si substrates were carried out up to 80 nm in depth, operating at 40 kV acceleration voltage. Ion dose was estimated by Faraday cup diagnostics. It was of the order of 1010 ions/cm2 per pulse.
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WEPCH188 | Compact Picosecond Pulse Radiolysis System Using Photo-cathode RF Gun | electron, injection, emittance, gun | 2373 | ||||
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A very compact picosecond pulse radiolysis system has been installed and operated at Waseda University. The system is composed of a laser photo-cathode RF gun as the pump source and stable Nd:YLF laser as the white light source to probe the reaction in the picosecond region. The white light generation is performed by the non-linear effect of intense laser light with the wavelength of 1047 nm into the water cell. The experimental results with the time resolution of 18 ps by examining the time profile of hydrated electron have been obtained. The system configuration will be also presented at the conference.
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WEPLS021 | The PLASMONX Project for Advanced Beam Physics Experiments | electron, photon, vacuum, emittance | 2439 | ||||
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The Project PLASMONX is well progressing into its design phase and has entered as well its second phase of procurements for main components. The project foresees the installation at LNF of a Ti:Sa laser system (peak power > 170 TW), synchronized to the high brightness electron beam produced by the SPARC photo-injector. The advancement of the procurement of such a laser system is reported, as well as the construction plans of a new building at LNF to host a dedicated laboratory for high intensity photon beam experiments (High Intensity Laser Laboratory). Several experiments are foreseen using this complex facility, mainly in the high gradient plasma acceleration field and in the field of mono-chromatic ultra-fast X-ray pulse generation via Thomson back-scattering. We present an innovative scheme of external injection of the SPARC beam into laser wake-field driven plasma waves. Detailed numerical simulations have been carried out to study the generation of short electron bunches, to be injected into plasma waves driven with adiabatically variable density in order to compress the bunch at injection and further accelerate it by preserving a small energy spread and good beam quality.
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WEPLS028 | Improvement of Electron Generation from a Laser Plasma Cathode through Modified Preplasma Conditions Using an Artificial Prepulse | electron, plasma, cathode, acceleration | 2448 | ||||
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We have been studying the effects of laser prepulses, plasma cavity formation, wave breaking processes in the laser plasma acceleration. It is important to control the preplasma conditions, so as to stabilize the laser plasma acceleration. The modification of the conditions of the laser plasma interaction through an artificial prepulse, magnetic fields, and/or gas density modulation will affect on the characteristics of accelerated electron beams. As the first step, we carry out experiments with an artificial prepulse. If a shockwave driven by the artificial prepulse matches the main pulse foccal position, localized wave breaking may occur effectively, and consequent electron generation will be enhanced. We use a pulse with 10% energy of the main pulse and 300 ps duration to be focused on the interaction point of the gas jet, to change the plasma distribution there. Using the single-shot diagnosis, we investigate the mechanism and technique to improve the properties of electron beams. We observed a strong correlation between the generation of monoenergetic electrons and optical guiding of the main pulse, during the interaction of 11 TW 37 fs laser pulse and He gas jet.
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WEPLS029 | Monoenergetic 200fs (FWHM) Electron Bunch Measurement from the Laser Plasma Cathode | electron, radiation, plasma, cathode | 2451 | ||||
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A laser plasma accelerator is the most promising approach to compact accelerators that can generate femtosecond electron bunches. It is expected that the electron bunch duration less than 100fs can be achieved owing to the high frequency of plasma waves. Since the time-resolution of the fastest streak camera is only 200fs, we have to use the coherent transition radiation (CTR) measurement or E/O (electro-optical) method. We plan to perform a single-shot measurement by getting the whole CTR spectrum by a IR polychromator in near future. As the first step forward it, we used a IR bolometer with different filters and obtained the average spectrum. We can generate monoenergetic electron bunches in the condition of laser intensity 3x1019W/cm2 and electron density 6x1019cm-3. The charge is estimated to be about 10pC using ICT (Integrated Current Transformer). The electron bunch accelerated by plasma waves penetrates 300um Ti-foil, and transition radiation is emitted. We measure CTR spectrum using a bolometer. Spectrum distribution of CTR depends on the electron bunch distribution, therefore we can evaluate the bunch duration from it. In the experiment, bunch duration can be estimated.
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WEPLS040 | Progress towards an Experimental Test of an Active Microwave Medium Based Accelerator | electron, resonance, controls, acceleration | 2463 | ||||
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We have been working on an experimental test of the PASER concept, where an active medium is used to provide the energy for accelerating charged particles. Initial theoretical work in this area focused on acceleration at optical frequencies; however we have identified a candidate active material operating in the X-band: a solution of fullerene (C60) in a nematic liquid crystal has been found to exhibit a maser transition* in this frequency range. The ability to employ a microwave frequency material simplifies the construction of test structures and allows beam experiments to be performed with relatively large beam emittances. We will report results on synthesis and testing of the active material using EPR spectroscopy, design and numerical simulations of bench test structures and plans for future beam experiments.
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*A. Blank et al. IEEE Trans. Microwave Theory and Techniques 46 (2137) 1998. |
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WEPLS044 | Design of a Superconducting Cavity for a SRF Injector | emittance, gun, cathode, electron | 2472 | ||||
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In a collaboration between BESSY, DESY, FZR, MBI and BINP a 3-1/2 cell superconducting RF electron gun is under development at the FZ - Rossendorf. The status of the project and the progress obtained in the last year is reported on this conference. The motivation for the design of a new gun cavity, presented in this paper, is the new FEL project at BESSY. This FEL is designed for a bunch charge of 2.5 nC and the transverse emittance should be comparable with that of the current SRF gun project. In order to compensate the high bunch charge a high electric field on the cavity axis is necessary. In the present paper we will present the design of a 1-1/2 cell cavity for a superconducting RF gun. The active length of the cavity (without beam tube) is 14.4 cm. For the magnetic peak field the conservative value of 130 mT is assumed. The obtained particle energy is 6.6 MeV, corresponding to an accelerating field strength of 45.6 MV/m . In the TESLA cavity the same magnetic peak field is connected with an accelerating field strength of approximately 31 MV/m. Tracking calculation of electron bunches are in progress and will be also reported.
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WEPLS050 | Experiments with Electron Cloud and Sources | electron, plasma, ion, injection | 2490 | ||||
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The Penning-Malmberg trap ELTRAP installed at University of Milano can provide electron clouds of several sizes for study of non-linear physics: length ranges from 0.15 to 1 m, while diameter is varied between 25 mm and 70 mm by changing the electron source: filament or planar spiral. Vortices develop both in trapped and flowing electron beams. Slow instabilities, due to the accumulation of ions inside the trap are observed and cured by clearing fields. Results as a function of plasma size are described. Plan to install a third laser modulated electron source and additional diagnostic are also summarized.
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WEPLS052 | High QE Photocathode at FLASH | cathode, gun, vacuum, electron | 2496 | ||||
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The RF gun-based photoinjector of the VUV-FEL/TTF at DESY continues to use high quantum efficiency (QE) photocathodes produced at LASA, Milano. To study the photocathode behavior during beam operation, an online QE monitoring tool has been installed. In this paper, we present the hardware and software setup for the online QE measurement and the results so far obtained. The measured QEs are usually higher than at TTF phase 1. We compare the QE values taken in the RF gun with data measured just after production with a continuous UV light source.
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WEPLS055 | Development of Double-decker Electron Beam Accelerator for Femto/attosecond Pulse Radiolysis | electron, gun, linac, emittance | 2505 | ||||
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The study of electron-induced reactions in femto/attosecond time region is very important for the next electron beam nanofabrication. Pulse radiolysis with time resolution of sub-picosecond, as a powerful method to study such reactions in materials, has been developed by using radio-frequency electron accelerators and ultrashort lasers. In Osaka University, a new concept of double-decker electron beam accelerator is proposed for opening next pulse radiolysis on femto/attosecond time scale. The double electron beams with time delay of 1.4ns (350ps x 4) and bunch charge of 0.5-0.6 nC were generated in a photocathode electron accelerator by injecting two laser pulses into the photocathode. The beam energy of the two beams was 31.7MeV. The transverse normalized emittance was 3~6 mm-mrad for both the beams. The front of them is converted to Cherenkov light and used as a probe light source, and the back is used as a pump source. Both electron pulses are generated by one accelerator, resulting in no time jitter between the pump electron bunch and the probe laser pulse.
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WEPLS057 | Equivalent Velocity Spectroscopy Based on Femtosecond Electron Beam Accelerator | electron, injection, gun, linac | 2511 | ||||
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A new femtosecond pulse radiolysis system, which is called as "Equivalent Velocity Spectroscopy (EVS)" based on a photocathode rf linear accelerator and a femtosecond laser, is developed in ISIR for the study of primly process and ultrafast electron-induced reactions for the nanofabrication. In order to achieve a high time resolution on femtosecond scale, a femtosecond electron beam bunch produced by a photocathode accelerator and a synchronized femtosecond laser were used. The electron bunch and laser pulse were injected with an angle determined by the refractive index of the sample. The electron bunch was also rotated with a same angle, resulting in the time resolution degradation due to the velocity difference between light and the electron in the sample is thus avoided. A jitter compensation technique with a femtosecond streak camera was used to reduce the time jitter between the electron bunch and laser pulse. Moreover, in EVS, a technique of double laser pulse injection was used to improve the signal to noise ratio due to the fluctuation of the laser intensity during the measurement.
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WEPLS058 | Femtosecond Single-bunch Electron Linear Accelerator Based on a Photocathode RF Gun | electron, gun, linac, emittance | 2514 | ||||
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A femtosecond single-bunch electron linear accelerator based on a photocathode rf gun was developed in Osaka University for the study of radiation-induced ultrafast physical and chemical reactions. A 32 MeV single electron bunch with a bunch length of 98 fs in rms was generated successfully in the linear accelerator with a magnet bunch compressor. The dependences of the bunch length and the transverse emittance on the bunch charge were investigated experimentally and theoretically. The higher-order effects in the magnetic field were studied and compensated successfully by using a nonlinear energy-phase correlation in the bunch produced in the linear accelerator. By using the femtosecond electron bunch, an equivalent velocity spectroscopy with a synchronized femtosecond laser, as a new method with femtosecond time-resolution, was developed for study of the ultrafast reactions or phenomena on the femtosecond time scale.
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WEPLS059 | The PHIN Photoinjector for the CTF3 Drive Beam | gun, CTF3, CERN, vacuum | 2517 | ||||
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A new photoinjector for the CTF3 drive beam has been designed and is now being constructed by a collaboration among LAL, CCLRC and CERN within PHIN, the second Joint Research Activity of CARE. The photoinjector will provide a train of 2332 pulses at 1.5 GHz with a complex timing structure (sub-trains of 212 pulses spaced from one another by 333 ps or 999 ps) to allow the frequency multiplication scheme, which is one of the features of CLIC, to be tested in CTF3. Each pulse of 2.33 nC will be emitted by a Cs2Te photocathode deposited by a co-evaporation process to allow high quantum efficiency in operation (>3% for a minimum of 40 h). The 3 GHz, 2 1/2 cell RF gun has a 2 port coupler to minimize emittance growth due to asymmetric fields, racetrack profile of the irises and two solenoids to keep the emittance at the output below 20 pi.mm.mrad. The laser has to survive very high average powers both within the pulse train (15 kW) and overall (200 W before pulse slicing). Challenging targets are also for amplitude stability (<0.25% rms) and time jitter from pulse to pulse (<1ps rms). An offline test in a dedicated line is foreseen at CERN in 2007.
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WEPLS060 | CLIC Polarized Positron Source Based on Laser Compton Scattering | CLIC, positron, damping, photon | 2520 | ||||
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We describe the possible layout and parameters of a polarized positron source for CLIC, where the positrons are produced from polarized gamma rays created by Compton scattering of a 1.3-GeV electron beam off a YAG laser. This scheme is very energy effective using high finesse laser cavities in conjunction with an electron storage ring. We point out the differences with respect to a similar system proposed for the ILC.
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WEPLS063 | Laser Driven Linear Collider | radiation, acceleration, collider, electron | 2523 | ||||
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We represent the details of scheme allowing long term acceleration with >10GeV/m. The basis of the scheme is a fast sweeping device for laser bunch. After sweeping the laser bunch has a slope with respect to the direction of propagation. So the every cell of accelerating structure becomes illuminated locally only for the moment, when the particle is there. Self consistent parameters allow considering this type of collider as a candidate for post-ILC era.
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THXPA03 | Laser Systems and Accelerators | electron, FEL, undulator, gun | 2728 | ||||
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The presentation will cover the use of laser systems in accelerators. Topics covered will be the use of lasers for the production of electron beam from photocathodes, timing and diagnostics, laser heater systems to control space charge effects, as seed systems. Challenges in terms of stability, pulse shaping, power and pulse lengths, wavelength range and tuning will be covered for the various aspects.
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THYPA01 | Overview of FEL Injectors | emittance, brightness, gun, electron | 2733 | ||||
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Future light sources based on high gain free electron lasers, require the production, acceleration and transport up to the undulator entrance of high brightness (low emittance, high peak current) electron bunches. Wake fields effects in accelerating sections and in magnetic bunch compressors typically contribute to emittance degradation, hence the photo-injector design and its operation is the leading edge for high quality beam production and for the success of the future light sources. RF guns, photo-cathode materials, laser pulse shaping and synchronization systems are evolving towards a mature technology to produce high quality and stable beams. Nevertheless reduction of thermal emittance, damping of emittance oscillations and bunch compression are still the main issues and challenges for injector designs. With the advent of Energy Recovery Linacs, superconducting RF guns have been also considered in many new projects as a possible electron source operating in CW mode. An overview of recent advancements and future perspectives in FEL injectors will be illustrated in this talk, including a comparison of merits and issues of RF compression versus magnetic compression techniques.
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THOPA01 | Formation of Electron Bunches for Harmonic Cascade X-ray Free Electron Lasers | electron, linac, CSR, radiation | 2738 | ||||
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A relatively long electron bunch is required for an operation of harmonic cascade free electron lasers (FELs). This is because they repeatedly employ a principle when the radiation produced in one cascade by one group of electrons proceeds ahead and interacts with other electrons from the same electron bunch in the next cascade. An optical laser is used to seed the radiation in the first cascade. Understandably the length of the electron bunch in this situation must accommodate the length of the x-ray pulse multiplied by a number of cascades plus a time jitter between the arrival time of the electron bunch and a seed laser pulse. Thus a variation of the peak current along the electron bunch as well as slice energy spread and emittance may affect the performance of the FEL. In this paper we analyze all possible sources affecting the distributions and interplay between them and show how desirable distributions can be produced. Results are illustrated with simulations using particle tracking codes.
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THOPA03 | An Integrated Femtosecond Timing Distribution System for XFELs | electron, free-electron-laser, controls, FEL | 2744 | ||||
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Tightly synchronized lasers and rf-systems with timing jitter in the few femtoseconds range are an important component of future x-ray free electron laser facilities. In this paper, we present an optical-rf phase detector that is capable of extracting an rf-signal from an optical pulse stream without amplitude-to-phase conversion. Extraction of a microwave signal with less than 10 fs timing jitter (from 1 Hz to 10 MHz) from an optical pulse stream is demonstrated. Scaling of this component to sub-femtosecond resolution is discussed. Together with low noise mode-locked lasers, timing-stabilized optical fiber links and compact optical cross-correlators, a flexible femtosecond timing distribution system with potentially sub-10 fs precision over distances of a few kilometres can be constructed. Experimental results on both synchronized rf and laser sources will be presented.
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*A. Winter et al. "Synchronization of Femtosecond Pulses", Proceedings of FEL 2005.**J. Kim et al. "Large-Scale Timing Distribution and RF-Synchronization for FEL Facilities", Proc. of FEL 2004. |
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THPPA01 | High-precision Laser Master Oscillators for Optical Timing Distribution Systems in Future Light Sources | feedback, electron, FEL, diagnostics | 2747 | ||||
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Abstract to be supplied
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THOBFI01 | A Sub 100 fs Electron Bunch Arrival-time Monitor System for FLASH | pick-up, electron, FEL, DESY | 2781 | ||||
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The stability of free-electron lasers and experiments carried out in pump-probe configurations depends sensitively on precise synchronization between the photo-injector laser, low-level RF-systems, probe lasers, and other components in the FEL. A measurement of the jitter in the arrival-time of the electron bunch with respect to the clock signal of a master oscillator is, therefore, of special importance. For this task, we propose an arrival-time monitor based on a beam pick-up with more than 10GHz bandwidth which permits measurements in the sub 100 fs regime. The RF-signal from the beam pick-up is sampled by an ultra-short laser pulse using a broad-band electro-optical modulator. The modulator converts the electron bunch arrival-time jitter into an amplitude modulation of the laser pulse. This modulation is detected by a photo detector and sampled by a fast ADC. By directly using the laser pulses from the master laser oscillator of the machine, any additional timing jitter is avoided. In this paper we present the layout of the system and first experimental results.
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THPCH010 | Electron Beam-laser Interaction near the Cathode in a High Brightness Photoinjector | electron, cathode, emittance, space-charge | 2805 | ||||
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The production of high charge short bunches in a high brightness photoinjector requires laser pulses driving the cathode with GW range peak power on a mm spot size. The resulting transverse electric field experienced by the electron beam near the cathode is of the order of 200-500 MV/m, well in excess of a typical RF accelerating field of 50-100 MV/m. We present here an analytical and computational study of the resultant beam dynamics. Simulations including the electron beam-laser interaction have been performed with the code HOMDYN taking into account the superposition of incident and reflected laser pulses as well as space charge fields. Under this conditions the emittance degradation is negligible, as predicted by analytical methods, but a longitudinal charge modulation occurs on the scale of the laser wavelength, in case of oblique incidence, driven by the longitudinal component of the laser field. Preliminary simulations up to the photoinjector exit show that charge modulation is transformed into energy modulation via the space charge field, which may produce enhanced microbunching effects when the beam is further compressed in a magnetic chicane.
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THPCH090 | Stabilization of the ILC Final Focus Using Interferometers | monitoring, quadrupole, target, simulation | 3000 | ||||
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We are developing a system of interferometers that can measure the relative motion between two objects (such as the two final focus quadrupoles) to a few nanometers using interferometric methods. Two instruments are developed at the John Adams Institute at University of Oxford: A distance meter to measure length changes and a straightness monitor to measure perpendicular shifts. We will present technique, results and resolutions of our distance meter prototype. We will also examine their applications at the ILC.
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THPCH139 | Development of an Ion Source via Laser Ablation Plasma | ion, plasma, extraction, target | 3119 | ||||
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Experimental results on the development of a laser ion source (LIS) are reported. LISs are particularly useful in ion accelerators, ion implanters and devices for electromagnetic isotope separation. A focused UV laser beam (0.1 - 1 GW/cm2 power density) was used to produce a plasma plume from a Cu target. Several aspects were investigated: ion angular distribution, energy distribution, ion extraction and charge loss due to ion recombination. Particular attention was devoted to avoid arcs during the extraction phase; it was accomplished by allowing the proper plasma expansion in a suitable chamber before the extraction gap. Diagnostics on free expanding plasma and extracted ions was carried out mainly by time-of-flight measurements, performed by means of Faraday cups and electrostatic spectrometers. At 18kV acceleration voltage, the ion beam current, measured along a drift tube at 147cm from the target, resulted modulated on ion mass-to-charge ratio and its maximum value was 220uA. The Cu+1 ion bunch charge was estimated to be 4.2nC. Ion implantation tests were successfully performed at high acceleration voltage (several tens kV), by using a simple experimental arrangement.
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THPCH140 | New Pulsed Current and Voltage Circuits Based on Transmission Lines | impedance, SLS, coupling | 3122 | ||||
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We present two novel circuits able to compress current or voltage pulse named current compressor circuit (CCC) and voltage compressor circuit (VCC), and two novel amplifier circuits able to double the current or voltage pulse. The compressing circuits were composed by a transmission line, l long and a storage line, l/2 long. The CCC compressed the current pulse by a factor of 2 doubling its intensity, while the VCC compressed the voltage pulse by a factor of 2 doubling its amplitude. The amplifying circuits were composed by a R0 transmission line closed on a set of two parallel or series storage lines which doubled the intensity of the pulses. The current pulse amplifier (CPA) had two R0/2 storage lines in parallel, while the voltage pulse amplifier (VPA) had two 2R0 storage lines in series. The storage line was half long with respect to the input-pulse. In both circuits, one storage line was characterized by an open extremity and the other line by a closed extremity. Connecting the storage lines to suitable load resistors, R0/4, and 4R0 for the CPA and VPA, respectively, a twice of the pulse intensity was obtained. The circuits were studied by computer simulations.
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THPCH149 | Active RF Pulse Compression using Electrically Controlled Semiconductor Switches | simulation, coupling, SLAC, plasma | 3140 | ||||
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In this paper, we present the recent results of our research on the ultra-high power fast silicon RF switch and its application on active X-Band RF pulse compression systems. This switch is composed of a group of PIN diodes on a high purity silicon wafer. The wafer is inserted into a cylindrical waveguide operating in the T·1001 mode. Switching is performed by injecting carriers into the bulk silicon through a high current pulse. Our current design uses a CMOS compatible process and the fabrication is accomplished at SNF (Stanford Nanofabrication Facility). The RF energy is stored in a room-temperature, high-Q 400 ns delay line; it is then extracted out of the line in a short time using the switch. The pulse compression system has achieved a gain of 11, which is the ratio between output and input power. Power handling capability of the switch is estimated at the level of 10MW.
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THPCH150 | Double-pulse Generation with the FLASH Injector Laser for Pump/Probe Experiments | SASE, FEL, radiation, polarization | 3143 | ||||
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The injector laser of the VUV-FEL at DESY, Hamburg, was modified to allow the generation of double-pulses, separated by a few cycles of the 1.3 GHz radio-frequency. Such double pulses are needed for driving the planned infrared/VUV pump/probe facility. Construction constraints of the facility will result in an optical path length about 80 cm longer for the infrared. Although the VUV can be delayed using normal-incidence multilayer mirrors at selected wavelengths, a fully flexible scheme is achieved by accelerating two electron bunches separated by more than the path length difference and then combine the infrared radiation from the first with the VUV from the second. This paper explains schemes for the generation of double-pulses with the laser system. It summarizes experimental studies of the effect on the operation of diagnostic instrumentation and on the tunability of the machine. Of special concern is the effect of wakefields on the quality of the second bunch, critical for achieving lasing.
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THPCH151 | Commissioning of the Laser System for SPARC Photoinjector | cathode, simulation, gun, emittance | 3146 | ||||
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In this paper we report the commissioning of the SPARC photoinjector laser system. In the high brightness photoinjector the quality of the electron beam is directly related to the features of the laser pulse. In fact the temporal pulse shape, the temporization and the transverse distribution of the electron beam is determined by the incoming laser pulse. The SPARC laser system is based on an amplified Ti:Sapphire active medium and the pulse shape is imposed by a programmable acousto-optics dispersive filter. The transfer-line has been designed to reduce the angular jitter and to preserve to the cathode the temporal and spatial features of the laser pulse. The laser system has been integrated with the accelerator apparatus. The diagnostics and the control system has been completed. We present the measured performances and the simulations we carried out.
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THPCH152 | Temporal Quantum Efficiency of a Micro-structured Cathode | cathode, electron, target, simulation | 3149 | ||||
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In this work the experimental and simulation results of photoemission studies for photoelectrons are presented*. The cathode used was a Zn disc having the emitting surface morphologically modified. Two different excimer lasers were employed like energy source to apply the photoelectron process: XeCl (308nm, 10ns) and KrF (248nm, 20ns). Experimental parameters were the laser fluence (up to 70 mJ/cm2) and the anode-cathode voltage (up to 20 kV). The output current was detected by a resistive shunt with the same value of the characteristic impedance of the sistem, about 100 ?. In this way, our device was able to record fast current signals. The best values of global quantum efficiency were approximately 5x 10-6 for XeCl and 1x 10-4 for KrF laser, while the peaks of the temporal quantum efficiency were 8x 10-6 and 1.4x10-4, respectively. The higher efficiency for KrF is ascribed to higher photon energy and to Schottky effect. Several electron-beam simulations using OPERA 3-D were carried out to analyze the influence of the geometrical characteristics of the diode. Simulating the photoemission by cathodes with micro-structures the output current was dependent on cathode roughness.
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*L. Martina et al. Rev. Sci. Instrum., 73, 2552 (2002). |
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THPCH153 | Production of Temporally Flat Top UV Laser Pulses for SPARC Photoinjector | target, emittance, diagnostics, electron | 3152 | ||||
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In the SPARC photoinjector, the amplified Ti:Sa laser system is conceived to produce an UV flat top pulse profile required to reduce the beam emittance by minimizing the non-linear space charge effects in the photoelectrons pulse. Beam dynamic simulations indicate that the optimal pulse distribution must be flat top in space and time with 10 ps FWHM duration, 1 ps of rise and fall time and a limited ripple on the plateau. In a previous work~\cite{loose} it was demonstrated the possibility to use a programmable dispersive acousto-optics (AO) filter to achieve pulse profile close to the optimal one. In this paper we report the characterization of the effects of harmonics conversion on the pulse temporal profile. A technique to overcome the harmonics conversion distortions on the laser pulses at the fundamental wavelength in order to obtain the target pulse profile is explained too. Measurements and simulations in the temporal and spectral domain at the fundamental laser wavelength and at the second and third harmonics are presented in order to validate our work. It is also described a time diagnostic device for the UV pulses.
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*H. Loos et al. "Temporal E-Beam Shaping in an S-Band Accelerator", Proc. Particle Accelerator Conference, p.642, 2005, Knoxville, TN, USA. |
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THPCH154 | Development of Pulsed Laser Super-cavity for Compact High Flux X-ray Sources | electron, photon, storage-ring, target | 3155 | ||||
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Pulsed-laser super-cavity is being developed at KEK-ATF for the application of a compact high brightness x-ray source based on Laser Compton Scattering. We use a Fabry-Perot optical cavity with a pulsed laser. The cavity increases a laser effective power, and at the same time, stably makes a small laser spot in side the cavity. In addition, the pulsed-laser gives much higher peak power. Thus, this scheme will open up a new possibility for building a compact high-brightness x-ray source, when collided with an intense bunched electron beam. We are now planning to build such an x-ray source with a 50MeV multi-bunch linac and a 42cm Fabry-Perot cavity using pulse stacking technology. We actually finished construction of the 50MeV linac and will start its operation in the spring, 2006. Development of the pulsed-laser super-cavity and future plan of our compact x-ray source will be presented at the conference.
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THPCH155 | High-quality Proton Beam Obtained by Combination of Phase Rotation and the Irradiation of the Intense Short-pulse Laser | ion, proton, target, electron | 3158 | ||||
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Ion production from laser-induced plasma has been paid attention because of its high acceleration gradient (>100GeV/m) compared with conventional RF accelerator. Its energy spectrum is Maxwell-Boltzmann distribution with high-energy cut-off, which limited its application. The phase rotation scheme, which rotates laser produced ions by an RF electric field synchronous to the pulse laser in the longitudinal phase space, was applied to proton beam up to 0.9MeV emitted from Ti foil with 3mm thickness irradiated by focused laser-pulse with peak intensity of 9 ´ 1017W/cm2. Multi-peaks with ~6% width (FWHM) were created and intensity multiplication up to 5 was attained around 0.6MeV region. The proton production process by the intense short-pulse laser has been optimized with use of time of flight measurement of proton beam detected by a plastic scintillation counter, which is specially shielded from the heavy background of electrons and X-rays induced by the intense laser. We have succeeded in on-line measurement of such a proton signal by the detector for the first time, which played an essential role for the investigation of phase rotation scheme.
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THPCH156 | SNS Transverse and Longitudinal Laser Profile Monitors Design, Implementation and Results | electron, SNS, SCL, linac | 3161 | ||||
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SNS is using a Nd:YAG laser to measure transverse profiles at nine-stations in the 186-1000 MeV Super-Conducting LINAC (SCL) and a Ti:Sapphire mode-locked laser to measure longitudinal profiles in the 2.5 MeV Medium Energy Beam Transport (MEBT). The laser beam is scanned across the H- beam to photo-neutralize narrow slices. The liberated electrons are directly collected to measure the transverse or longitudinal beam profiles. We have successfully measured the transverse and longitudinal profiles at all stations. The SCL laser system uses an optical transport line that is installed alongside the 300 meter super-conducting LINAC to deliver laser light at nine locations. Movement of the laser light in the optical transport system can lead to problems with the profile measurement. We are using telescopes to minimize the oscillations and active feedback system on mirrors to correct the drifts and movements. In this paper we present our implementation and beam profiles measured during SCL commissioning. We also discuss future improvements, drift/vibration cancellation system, as well as plan to automate subsystems for both the transverse and the longitudinal profiles.
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THPCH158 | A Phased-locked S.A.M. Mode-locked Laser for the ELSA Photoinjector | ELSA, electron, photon, linac | 3164 | ||||
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A new laser oscillator has been developed for the ELSA photoinjector. It is a fibered-diode-pumped mode-locked Nd:YVO4 laser, with a completely passive cooling design. Mode-locking is achieved by a saturable absorber mirror. Such a passive laser oscillator must be synchronized with the ELSA electron bunches. A phased-locked loop has been developed for that purpose. We present the main design aspects resulting from the high stability requirement of ELSA. The first electron spectra measurements show the high level of energy stability achieved. We also present improvements in the laser injection system leading to a higher transverse stability, a more uniform cathode illumination, and a better transmission of the whole system.
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THPCH161 | Status of the Polarized Electron Gun at the S-DALINAC | electron, gun, cathode, quadrupole | 3173 | ||||
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Aiming at an extension of the experimenting capabilities for nuclear structure physics at low momentum transfer at the superconducting Darmstadt electron linear accelerator S-DALINAC, a polarized electron gun is being constructed. The new injector will be able to supply the S-DALINAC with 100 keV polarized electrons and should complement the present, unpolarized thermionic source. The design requirements are a degree of polarization of at least 80%, a mean current intensity of 0.06 mA and a 3 GHz cw structure. The basic design of the gun was adapted from the source of polarized electrons at MAMI, Mainz*, and optimized in various simulations. The active material is a strained layer GaAs crystal which is exposed to an 830 nm pulsed laser beam. We report on the status of the polarized source, the preparation setup and a test beam line.
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*K. Aulenbacher et al., Nucl. Instrum. Meth. A 391, 498 (1997). |
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THPCH165 | ERLP Quantum Efficiency Scanner | cathode, ERLP, controls, linac | 3179 | ||||
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The Energy Recovery Linac Prototype (ERLP) under construction at Daresbury Laboratory will utilise a photoinjector as its electron source. In order to characterise the performance of the photo-cathode wafer, a low power laser is scanned across its surface and the resultant current measured to build up a map of the quantum efficiency of the wafer.
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THPCH182 | Control of the Geometrical Conformity of the LHC Installation with a Single Laser Source | LHC, controls, survey, CERN | 3224 | ||||
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A large and complex accelerator like LHC machine needs to integrate several thousand different components in a relatively limited space. During the installation, those components are installed in successive phases, always aiming to leave the necessary space available for the equipment which will follow. To help ensure the correct conditions for the installation, the survey team uses a laser scanner to measure specific areas and provides this data, merged together in a known reference system, to the integration team who compares the results with the 3D CAD models. This paper describes the tools and software used to rebuild underground zones in the CATIA environment, to check interferences or geometrical non-conformities, as well as the procedures defined to solve the identified problems.
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THPLS015 | Spectral Fingerprints of Femtoslicing in the THz Regime | electron, resonance, radiation, undulator | 3302 | ||||
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Femtosecond (fs) THz pulses are observed as a consequence of laser-induced energy modulation of electrons in the BESSY II storage ring in order to generate fs x-ray pulses via femtoslicing*. The THz pulses are spectrally characterized by step-scan and rapid scan FTIR spectroscopy. The temporal shape of the laser-induced density modulation is reconstructed from the THz spectra. It is studied as a function of laser and storage ring parameters and monitored over several revolutions. The results are compared with numerical simulations. The THz spectra acquired over a few seconds are used to optimize the laser parameters for achieving minimum x-ray pulse lengths in femtoslicing experiments.
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*A. Zholents and M. Zoloterev, PRL 76 (1996), 912. |
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THPLS016 | Bunch Shape Diagnostics Using Femtoslicing | electron, CSR, radiation, undulator | 3305 | ||||
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Laser-energy modulation of relativistic electron bunches as needed for the BESSY femtosecond (fs) x-ray source is accompanied by the emission of fs THz pulses*. The total THz intensity probes the square of the longitudinal particle density within a slice of ~50 fs length (fwhm). The bunch shape can be directly monitored while sweeping the time delay between laser and bunch clock. The method is demonstrated for bunch lengths between 3 and 30 ps (rms) in different operation modes of BESSY II. The use of THz signals from successive turns and the influence of periodic bursts of coherent synchrotron radiation, which lock to the laser pulse under certain conditions, are discussed. The method is used for setting up and stabilizing the temporal overlap between a fs-laser and a relativistic electron bunch.
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*K. Holldack et al., Phys. Rev. Lett. (2006), accepted Dec. 2005. |
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THPLS040 | Present Status of the UVSOR-II | electron, undulator, emittance, FEL | 3374 | ||||
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UVSOR electron storage ring, which was a 2nd-generation synchrotron radiation (SR) light source for VUV and soft x-ray region, has been renewed as UVSOR-II at the beginning of 2003. Because of the improvement, the beam emittance has been reduced from 165nm-rad to 27nm-rad, and longer straight sections with smaller vertical betatron functions have been provided. In addition to a helical/linear undulator, two in-vacuum undulators have been installed in the long straight sections at the improvement. New variably polarized undulator will be also installed in summer 2006. Improvement of booster synchrotron will be also performed in summer 2006 with aiming to top-up operation in the future. Now UVSOR-II has been operated in 750MeV with the emittance of 27nm-rad in daily users runs. Not only the development of high quality SR beams but also basic investigations for new light source have been performed; development of storage ring FEL and investigation of intense THz burst SR. Bunch slicing experiment with a Ti:Sa laser (800nm) has also been started since 2005, and experiments for coherent harmonic generation and coherent SR generation with the laser-beam interaction have been performed.
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THPLS041 | Observation of Intense Terahertz Synchrotron Radiation produced by Laser Bunch Slicing at UVSOR-II | electron, radiation, CSR, synchrotron | 3377 | ||||
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We have performed electron bunch slicing experiments using a femto-second high power pulse laser in the UVSOR-II electron storage ring. As the pulse laser system we have used a Ti:Sa laser whose wavelength is 800 nm, typical pulse duration is 100 fs, pulse repetition is 1 kHz and typical average power is 2W. The laser is operated in mode-locked condition and synchronized with the electron beam revolution. The laser pulse is injected into an undulator section and it goes along with the electron bunch. By adjusting the radiation wavelength of the undulator to the laser wavelength, the electron beam energy can be partially modulated in the electron bunch. We have observed THz synchrotron radiation (SR) light from a bending magnet that is downstream of the interaction region. The SR light contains extremely intense THz pulse radiation that is synchronized with the laser injection. The extremely high intensity strongly suggests that the THz pulses are coherent synchrotron radiation from the electron bunch with a hole because of the laser-beam interaction.
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THPLS044 | Preliminary Experiment of the Thomson Scattering X-ray Source at Tsinghua University | electron, scattering, photon, linac | 3386 | ||||
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A preliminary experiment of the Thomson scattering x-ray source is being planned and constructed to generate short-pulsed, tunable x-rays in the range of ~4.5 kev by Thomson scattering of laser photons from a relativistic electron beam. Laser photons of ? = 1064 nm are Thomson backscattered by a 16MeV electron beam from a 16MeV Backward Travelling Wave (BTW) electron linac. The laser is derived from a 2J,10ns Nd:YAG laser. The parameters of electron beam and laser have been measured. The simulated and experiment results are described in this paper.
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THPLS062 | Sub-picosecond X-ray Source FEMTO at SLS | SLS, undulator, wiggler, storage-ring | 3427 | ||||
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The FEMTO source at the SLS (Swiss Light Source) employs laser/e-beam 'slicing' to produce sub-picosecond x-ray pulses for time resolved pump/probe experiments. The final design of the source, the status of construction and commissioning as well as the first experimental results will be presented.
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THPLS092 | Nb-Pb Superconducting RF-Gun | dipole, cathode, DESY, emittance | 3493 | ||||
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We report on the status of an electron RF-gun made of two superconductors: niobium and lead. The presented design combines the advantages of the RF performance of bulk niobium superconducting cavities and the reasonably high quantum efficiency of lead, as compared to other superconducting metals. The concept, mentioned in a previous paper, follows the attractive approach of all niobium superconducting RF-gun as it has been proposed by the BNL group. Measured values of quantum efficiency for lead at various photon energies, analysis of recombination time of photon-broken Cooper pairs for lead and niobium, and preliminary cold test results are discussed in this paper.
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THPLS093 | Status of the Photocathode RF Gun System at Tsinghua University | gun, cathode, scattering, BNL | 3496 | ||||
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An S-band high gradient photocathode RF gun test stand is in construction process at Tsinghua University. The photocathode RF gun test stand is a primary step of a femtosecond hard x-ray source based on Thomson scattering. The photocathode RF gun system adopts Ti:Sap laser, BNL IV type 1.6 cell RF gun, compact compensation solenoid. We foresee to conduct investigations on the thermal emittance contribution of surface roughness, the emittance compensation technique under various laser shape and its application to Thomson scattering x-ray source. Except for the transportation of laser, correction of laser front for glazing incidence and laser pulse shaping system, other parts of the photocathode RF gun test stand have been constructed, and we can start very primary experiment on the RF gun test stand, such as measurements of dark current, QE and energy of the beam. The experimental results are reported.
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THPLS097 | Model of the CSR Induced Bursts in Slicing Experiments | CSR, electron, undulator, SLAC | 3502 | ||||
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In a recent experiment on 'femtoslicing' at the Advanced Light Source in LBNL, it has been observed that the beam slicing initiates correlated bursts of coherent synchrotron radiation (CSR) of the beam. In this paper, we suggest a model describing such bursts. The model is based on the linear theory of the CSR instability in electron rings. We describe how an initial perturbation of the beam generated by the laser pulse evolves in time when the beam is unstable due to the CSR wakefield. Although this model does not give quantitative predictions, it qualitatively explains the evolution of the induced CSR bursts.
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THPLS104 | Optimization Studies of the FERMI@ELETTRA Photoinjector | emittance, electron, cathode, gun | 3520 | ||||
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In the framework of the FERMI@ELETTRA project the electron beam characteristics strongly depend from the two operating modes: FEL1 (100nm-40nm) with a photon pulse around 100fs and FEL2 (40nm-10nm) with a long photon pulse (~1ps) having a high resolution spectral bandwidth. We present the multi-particles tracking code results concerning the photoinjector, which includes the RF gun and the first two accelerating sections, describing two possible electron bunch lengths, satisfying the two FEL operation modes. The injector optimization relative to the two options, aimed to produce a very low projected emittance (around 1 mm mrad) with a uniform behavior of the slice parameters (emittance and energy spread) along the bunch, is described in this paper. Moreover sensitivity studies, time and energy jitters estimations are presented for both cases.
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THPLS105 | Characterization of the SPARC Photo-injector with the Movable Emittance Meter | emittance, cathode, space-charge, diagnostics | 3523 | ||||
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As a first stage of the commissioning of SPARC accelerator a complete characterization of the photo-injector is planned. The objective is the optimization of the RF-gun setting that best matches the design working point and, generally, a detailed study of the emittance compensation process providing the optimal value of emittance at the end of the linac. For this purpose a novel beam diagnostic, the emittance-meter, consisting of a movable emittance measurement system, was conceived and built. This paper presents the results of the first measurements with the emittance-meter showing the characteristics and the performance at the SPARC photo-injector.
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THPLS108 | Performance Test of RF Photo-Cathode Gun at the PAL | gun, emittance, electron, cathode | 3529 | ||||
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A RF photo-cathode (RF PC) gun with 1.6 cell cavity is installed for the fs-FIR (Femto-second Far Infrared Radiation) facility being built at the Pohang Accelerator Laboratory (PAL). A short, intense, and low emittance electron beams are produced by the RF PC gun. Performance test of the gun is done include the measurement of RF chraterizations such as a resonant frequency, a mode separation, and etcs. The diagnostics of the beam according to the beam parameters such as phase, charge, and energy, and emittance are done. In this article, we present the measurement results of the RF charaterizations and the beam parameter diagnostics of the RF PC gun at the PAL.
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FRYBPA01 | Overview of Single Pass Free Electron Lasers | electron, radiation, FEL, undulator | 3636 | ||||
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The presentation will cover world wide status of single pass free electron lasers. A general status will be given of the projects. Common themes will be discussed, as will the challenges of these themes. Unique characteristics of individual projects will also be covered. Here the emphasis will be on a description of novel and challenging techniques: for example examples seeding of the FEL, different types of guns for high brightness electron beam production, very short or very long pulse production, etc.
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Transparencies
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